NOTES ON THE PURIFICATION OF SEWAGE. XV. 



Oeek and Cook's River. • Into these mains the porous lines 

 deliver the filtered sewage, the whole being controlled by valves 

 4>n the main outlets. 



Results of Treatment. — Western and Southern Systems — There is 

 no doubt that without this, or an equally rapid system of filtration, 

 the whole of the raw sewage arriving on the farm could not be 

 disposed of on the area mentioned, and it is this rapidity of 

 disposal which is the controlling factor in the whole scheme at 

 present in vogue; but when the final state of the effluent comes 

 to be considered it is a question whether a higher degree of puri- 

 fication could not be obtained at a much less cost and on a smaller 

 area. The whole of this filtration area is divided up into different 

 beds with distributing pipes running down the dividing banks 

 having ofllet pipes, by means of which the beds are flooded. The 

 sewage then percolates down through the fine sand and finds its 

 way into sub-drains, and thence to the outlets discharging into 

 the river. Its condition is then neither more nor less than finely 

 screened sewage, having a low degree of purification due to 

 anaerobic agencies, but is then no w T orse than the river into 

 which it discharges, hence no harm is done. 



The very essence of sewage purification is the ultimate destruc- 

 tion of undesirable matter, and as no matter what you do with 

 sewage, it is eventually rendered innocuous by nature, instead of 

 retarding it the object should rather be to make the conditions 

 so favourable that the decomposition is conducted on lines 

 resembling those of nature as much as possible. The lime process 

 is the very reverse of this, as by the use of large quantities of 

 lime the living organised bodies such as bacteria are destroyed, 

 and seeing that such bacteria give rise to that phenomena known 

 ^.s putrefaction, it simply means that until the effect of the lime 

 has worn off the oxidising organisms cannot get to their work 

 and decomposition which must come, is thereby retarded. Even 

 if the lime process as generally carried out were a success, as far 

 as the final state of the effluent is concerned, the question of cost 



